The glass of a motor-vehicle window or sunroof must be mounted solidly enough that it can withstand the buffeting of the high-speed winds created during road travel, and it also must seal very tightly. Furthermore it must present a neat appearance and have a low profile for minimal wind resistance.
A typical system is described in German patent 197 24 592 of L. Hartmann imbeds the inside edge of the normally metallic frame and the outside edge of the glass pane in a polyurethane seal strip that is formed in situ around the parts. To this end the edges of the frame and pane must be encased between a pair of mold parts forming a cavity at the edges. This cavity is filled with liquid polyurethane that is allowed to cure, whereupon the mold is open. While this system does produce a very neat and strong joint, it makes it virtually impossible to replace the glass if necessary. Thus if the glass is broken, an entire new frame assembly is needed.
A partial solution to this problem is seen in German patent document 195 26 283 of J. Siebold. It provides separate seal strips on the window and frame edge and uses screws to secure the two parts together. This arrangement is fairly complex and the seal is often inadequate. Furthermore the parts are difficult to assemble.